The field of the invention is electrical junction boxes and conduit junction boxes. Most building codes require electrical wiring to be enclosed in electrical conduit which are coupled to one another by electrical junction boxes. A typical junction box has a hollow body with at least one open side. A junction box has conduit coupling hubs extending through the walls of the box and an interior space that is accessible through the open sides of the box. Wires extend through the conduit into the junction boxes where they are commonly spliced or joined. The open sides of the junction box are then closed with removable covers that are attached to the body of the junction box with screws. Examples of prior electrical conduit systems and junction boxes are described in U.S. Pat. Nos. 1,741,358; 2,208,558; 2,398,782 and 5,169,013.
A common shape for a conduit box is one with a generally oblong body, one open longitudinal side, curved ends and conduit coupling hubs at various locations on the body. Conduit boxes are assigned various type designations (such as LL, LB, LR, T, X, E and C) depending on the number and locations of these coupling hubs. Conduit box specifications including dimensions, interior volume and maximum numbers of conductors are set forth in Article 370 of the National Electrical Code Hand Book, Twenty-Fourth Edition.
Conduit boxes have bodies that form a separate portion of the conduit or tubing system. The inside of a conduit box is accessed through a removable cover. Large case or sheet metal boxes are not classified as conduit boxes. Conduit boxes cannot be concealed or buried underground. Under National Electrical Code, they must be either above ground or, if underground, must be accessible at all times. They can be installed indoors or outdoors and in damp locations, are dust proof and are coated inside and out to prevent corrosion.
Conduit box bodies may have threaded or non-threaded hubs or a combination of each. The oblong shape of some conduit junction boxes increase the ease of routing and pulling wire through the conduit junction box, which prevents damage to the wire's insulation by preventing the wire from sliding over sharp corners.
A common problem with conduit junction boxes installed outdoors is that they are subject to corrosion, which is accelerated by electrolysis. This is due to the fact that they are often exposed to adverse environmental conditions and electrical current. The result is that the removable cover and/or the attachment screws can corrode. When this occurs, it can be very difficult if not impossible to completely remove the attachment screws from the conduit junction box without damaging the conduit junction box's threaded holes. When corrosion damages or renders the threaded holes unusable, the conventionally designed removable cover can no longer be installed on the junction box and the junction box must be replaced. Replacing the entire junction box can be time consuming and costly, in part because all of the electrical connections inside the junction box must be rewired.
It would be highly desirable to provide an alternatively designed replacement cover that can be installed on new conduit junction boxes or on inservice conduit junction boxes with damaged or otherwise unusable threaded holes. The present invention obtains these results. For the replacement cover that comprises this invention, even if the screws corrode, removal and replacement may be performed without having to repair or replace the electrical junction box. Therefore, it becomes cheaper, easier and quicker to open, close and refit the conduit junction box with the new replacement cover.